Mutation Research 632 (2007) 78–88 Inflammatory response and genotoxicity of seven wood dusts in the human epithelial cell line A549 Jette Bornholdt a , Anne T. Saber a , Anoop K. Sharma a , Kai Savolainen b , Ulla Vogel a , H˚ akan Wallin a,∗ a National Research Centre for the Working Environment, Lersø Park All´ e 105, DK-2100 Copenhagen, Denmark b Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, 00250 Helsinki, Finland Received 4 December 2006; received in revised form 27 March 2007; accepted 18 April 2007 Available online 21 May 2007 Abstract Exposure to wood dust is common in many workplaces. Epidemiological studies indicate that occupational exposure to hardwood dusts is more harmful than to softwood dusts. In this study, human epithelial cell line A549 was incubated with well-characterized dusts from six commonly used wood species and from medium density fibreboard (MDF), at concentrations between 10 and 300 g/ml. After 3 and 6 h of incubation, genotoxicity was assessed by measurement of DNA damage with the single-cell gel electrophoresis (comet) assay and inflammation was measured by the expression of IL-6 and IL-8 mRNA and by the amount of IL-8 protein. There was a 1.2–1.4-fold increase in DNA strand breaks after incubation with beech, teak, pine and MDF dusts compared with the levels in untreated cells, but after 6 h only the increase induced by the MDF dust remained. Increased expression of cellular IL-6 and IL-8 mRNA was induced by all of the wood dusts at both times. Similar to IL-8 mRNA expression, the amounts of secreted IL-8 protein were elevated, except after incubation with oak dust, where a marginal reduction was seen. On the basis of the effects on IL-8 mRNA expression, the wood dusts could be divided into three groups, with teak dust being the most potent, MDF, birch, spruce and pine being intermediate, and beech and oak being the least potent. The induction of DNA strand breaks did not correlate well with the interleukin response. In conclusion, all wood dusts induced cytokine responses, and some dusts induced detectable DNA damage. The inflammatory potency seemed intermediate for dusts from the typical softwoods spruce and pine, whereas the dusts from species linked to cancer, beech and oak, were the least inflammatory. The variation of the effects induced by different wood dusts over time indicates that the DNA damage was not secondary to the cytokine response. Although hardwoods are often considered more harmful than softwoods by regulatory agencies, the current experiments do not provide evidence for a clear-cut distinction between toxicities of hardwood and softwood dust. © 2007 Elsevier B.V. All rights reserved. Keywords: Wood dust; Inflammation; DNA damage; A549 cell line ∗ Corresponding author. Tel.: +45 39 16 52 26; fax: +45 39 16 52 01. E-mail address: hwa@nrcwe.dk (H. Wallin). 1. Introduction Wood dust is one of the most common occupational dust exposures. Worldwide, approximately 13 million people were occupied in the forestry sector and about 3.5 million people in the furniture industry in year 2000. This means that about 0.4% of the total labour force were 1383-5718/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.mrgentox.2007.04.016